The race was put under caution and Ward, 20, exited his car, walked onto the track and gestured toward Stewart, police say.

Stewart was behind another car on the caution lap. The car ahead was able to avoid Ward, but Stewart hit Ward with his car.

Emergency personnel at the track treated Ward. He was sent to a hospital, where he later died.

"There aren't words to describe the sadness I feel about the accident that took the life of Kevin Ward Jr.," Stewart said in a statement released by NASCAR. "It's a very emotional time for all involved, and it is the reason I've decided not to participate in today's [Sunday's] race at Watkins Glen. My thoughts and prayers are with his family, friends and everyone affected by this tragedy."

"We appreciate the prayers and support we are receiving from the community, but we need time to grieve and wrap our heads around all of this," the Ward family said in a statement reported by WHAM-TV (ABC, Rochester, N.Y.).

Police say Stewart has cooperated with the investigation.

"(Stewart) was visibly shaken by this incident," Sheriff Philip Provero, R-Ontario County, N.Y., says. "There are no charges pending at this time. This is, right now, being investigated as an on-track crash."

The sheriff's office has made a plea for any amateur video from fans to be submitted to police to help in the investigation.

Stewart, 46, of Columbus, Ind., routinely races at dirt tracks the night before Sprint Cup races. A year ago, the three-time Cup champion broke his leg in a dirt track race, missing the remaining 15 races of the Cup schedule.

"A tragic accident took place last night during a sprint car race in which Tony Stewart was participating," Stewart-Haas Racing, which Tony Stewart co-owns, said in a statement. "Tony was unhurt, but a fellow competitor lost his life. Our thoughts and prayers go out to his family and friends. We’re still attempting to sort through all the details and we appreciate your understanding during this difficult time."

"Our thoughts and prayers go out to the family, friends, and fellow competitors of Kevin Ward Jr.," NASCAR said in a statement. "We support Tony Stewart's decision to miss today's race and we will continue to respect the process and timeline of the local authorities and will continue to monitor this situation moving forward."

Regan Smith drove Stewart's No. 14 car in his place.

Ward, a Port Leyden, N.Y., native, raced for his father's racing team, Kevin Ward Racing. The younger Ward began racing go-karts at age 4, and would become a championship driver in micro-sprint and sprint car racing.

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